Method of making an electrical connector



P 1965 J. L. YONKERS 3,206,833

METHOD OF MAKING AN ELECTRICAL CONNECTOR Filed July 23, 1963 MW.cfofzzzfi YOVZ/ff/ZS ROBERT L.KA HN ATTY United States Patent 3,206,833METHOD OF MAKING AN ELECTRICAL CONNECTOR John L. Yonkers, Northbrook,Ill. Electro-Appliance Co., Inc., 1915 N. Elston St., Chicago, Ill.)Filed July 23, 1963, Ser. No. 296,980 1 Claim. (Cl. 29155.5)

This invention relates to an electrical connector and more particularlyto a connector using a tapered helical spring disposed within aninsulating body. The invention also relates to a method of making thenew connector.

Wire connectors generally to which this invention relates have a taperedmetal helical spring into which wires to be connected are twisted. Thisspring is disposed within a rigid insulating body. This construction hassome serious disadvantages. For one thing, twisting a wire connectorover a number of copper wires makes it necessary for the rigidinsulation to be strong enough to withstand the force exerted by thespring in tending to go over the wires to be connected. Considerableforce tending to expand the coil diameters of the small end against thehousing body is created. This may crack the housing body. The use ofpliers on such connectors can be dangerous. The bite of the jaws of aplier on the insulating body may crack the same. Also the use of pliersto twist the wires deeper into the connector may result in cracking theconnector body as pointed out. In addition, the spring within thehousing body may become so firmly attached to the wires to be connectedthat the spring is separated from the insulating body and permits thebody to drop or separate.

The present invention provides a wire connector having a spring membercompletely disposed within an insulating housing, which need not berigid and is preferably flexible. The spring member has a helical springconnector portion which is preferably though not necessarily tapered andan anchor portion which is firmly attached to the insulating housingbody. The helical connector spring portion is available for use as aconnector for wires to be disposed therein but itself is not attached tothe housing body. The insulating body, when flexible, provides a numberof substantial advantages. One is that the connector and wires to beconnected may be turned relative to each other over a range which is notsharply defined without damage to the insulating housing body. Inaddition, it is diflicult to destroy the connection between the anchorportion of the spring member and the housing body. Hence the newconnector, whenever applied to wires for connection purposes, will notexpose the joined wires. In addition, as will be apparent later, the newconnector permits the spring coils to readily adapt themselvescompletely to wires to be connected.

The invention generally provides that coils or turns making up theanchor portion of a spring member have plastic molded completely aroundthe individual wires for anchoring the spring to the insulating bodyhousing. The remainder of the tapered helical spring is free of theplastic and is available for connecting purposes, the entire springbeing disposed within the insulating body housing. In general, it ispreferred to have the spring conneetor portion to be anchored at thelarge end of a tapered helical spring. This disposition has advantageswhich will be apparent after the invention has been described. However,the anchor portion of the spring may be at either end or at someintermediate portion of the helical spring. Generally, the turn or turnsof the helical spring forming the anchor portion thereof will havesulficiently large diameter so that the anchor turns will clear the barewires being joined. In other words, the function of the anchor portionof the spring is purely for anchor- 3,206,833 Patented Sept. 21, 1965age purposes and is not concerned with electrical connecting.

The procedure for making connnectors embodying the present inventioninvolves two steps which are essential for quantity production. One stepinvolves the application of a priming coating of plastic to the anchorportion only of the helical coil spring. In its simplest form, thisinvolves the application of an epoxy resin coating to the anchor turnsof the spring only. The other step involves the application to theentire spring member, including the primed anchor portion, of a plasticcoating having the property of not adhering to unprimed metal and alsohaving desired physical properties of toughness and electricalinsulation. The second step is most conveniently accomplished by havinga mandrel carry the spring member and shaped to fill the space withinthe turns of the connector portion while leaving space between themandrel and anchor turns. Plastic is thereupon applied to the entirespring member and mandrel. The mandrel is of a material to which theplastic will not adhere. The plastic may be applied by dip-coating or bya variation known as fluidized bed coating. .The dip coating procedureutilizes a liquid bath of a plastic such as polyvinyl chloride (PVC) orvinyl latex into which the mandrel and spring, at a suitably hightemperature, are dipped and withdrawn. utilizes a finely divided solidplastic, as polyethylene, which is blown over the work to be coated.

'Such plastic materials used for coating metals in general do not adherestrongly to metal, s0 that unprimed portions of the spring member willnot be firmly secured to the plastic. However, many-if not mostof theplastics used for coating will bond to an epoxy resin primer coating.

'For a more complete description of the invention, reference will now bebe made to the drawings wherein:

FIGURE 1 shows a perspective view, with a portion broken away, of aconnector embodying the present invention, three wires to be joinedbeing shown in dotted form.

FIGURE 2 is a section on line 22 of FIGURE 1, with the addition of amandrel for illustrating the connector immediately after the clippingprocedure for mak: ing the same.

FIGURE 3 is a perspective view of the spring.

FIGURE 4 is a view in diagrammatic form illustrating a means fordip-coating a spring member carried by a mandrel.

The new connector has a metal spring member which includes helicalspring 10 here shown as of the tapered type having small end 11 andlarge end 12. The spring metal used may be brass, copper plated steel,phosphor bronze, or any of the metals used in connectors of this generaltype presently available on the market. Tapered helical spring 10 isillustrated as having a generally smooth taper for most of the length ofthe spring, although this is not essential. In the form illustratedhere, spring .10 has about two large turns 13 and 14 extending fromlarge end 12. Turns 13 and 14 have a large diameter than turn 12, forexample, which is the largest diameter turn of the uniformly taperedbody portion of the spirng. Turns or coils 13 and 14 function as theanchor portion of the spring member while spring 10 functions as theconnector portion. The pitch of end turns 13 and 14 is increased overthat of portion 10 so that these end turns or coils are spaced from eachother along the axis of the spring member a short distance. The amountof spacing is unimportant so long as there is suflicient space forplastic to be disposed between the coils of the anchor portion of thespring member.

Similarly, the increase in diameter of the coils of the anchor portionis not important with regard to the amount The fluidized bed coatingprocedure of increase except that the increase should be sufficient sothat the end turns forming the anchor portion of the spring can becompletely embedded in plastic, while leaving the rest of the springfree. However, the change, insofar as the pitch and diameter of theanchor turns of the spring member, can be eliminated with flexibleplastic and the end turns of a helical spring having a more or lessuniform taper can be utilized as the anchor portion. While the turns ofspring connector portion are shown as being closely spaced, that is notessential.

The completed connector, as illustrated in FIGURES 1 and 2, has anchorportion turns 13 and 14 securely bonded to plastic housing body 20. Thisis obtained by priming anchor turns 13 and 14 with a thin layer of epoxyresin. It is understood that the anchor portions to be primed must besuitably prepared to be clean and free of grease so that the epoxy resinwill bond to the metal. The turns of connector spring portion 10,beginning with turn 12 and ending with small end 11 are not bonded toplastic 20 by the simple expedient of leaving the metal un primed. Asillustrated in FIGURE 2, plastic housing body 20 has portion 21 which isdisposed within one or two end turns of the spring at the small end.This can be avoided if desired, but is generally not objectionable.

By having the anchor portion at an end of the spring member, a simpledipping operation can apply liquid epoxy resin to those turns only.Thereafter the spring member is heated to cure the primer layer. In someinstances, heating the primer layer may not be necessary, depending uponthe resin used.

The plastic for body 20 can be any one of a number of plastic materialswhich do not bond to unprimed metal and are tough and can be applied asa coating. Examples of such plastics are polyvinyl compounds,particularly the chlorides, nylon, polyethylene, rubber. Polyvinylchloride is widely used for dip-coating and is excellent for use here.

In order to manufacture the connector thus far described, it ispractically necessary to use a mandrel. If dip-coating is to beutilized, then mandrel 25 will have to be of metal for retaining andconducting heat at a desired rate. Thus mandrel 25 may be of aluminum,copper, brass or steel. Mandrel portion 27 is shaped to fit snuglyWithin connector portion 10 of the spring member. Mandrel portion 27 haspart 28 which is disposed to clear anchor portion turns 13 and 14 of thespring member. In order to prevent excessive buildup of plastic at thisregion, the mandrel may be undercut at region 28 and provided withcollar 30 of a material like Teflon. This material, as is well known,can withstand a much higher temperature than most plastics and has agreasy surface to which most plastic materials will not adhere. Heatexchange between the mandrel metal and the plastic being applied isaffected. Build-up of the plastic coating material can be controlled.However, collar 30 may be omitted if desired or may be of metal.

With mandrel 25 disposed within spring connector portion 10 asillustrated in FIGURE 2, the formation of plastic housing 20 can beinitiated. In dip-coating, mandrel 25 is suspended to be in a verticalposition as illustrated in FIGURE 4. The mandrel and spring arepreheated to about 400 F. for P.V.C. dip-coating and then dipped intobath 34 of liquid P.V.C. maintained at a constant temperature and level.The mandrel and spring are quickly dipped into the bath to the desireddepth and are pulled upwardly from the bath at a predetermined rate.Whenever the withdrawal rate is slowed, the amount of plastic depositedaround the mandrel and spring will increase in thickness. As a result,many shapes for insulating body 20 are possible. The preheating step maybe utilized for curing the epoxy resin primer layer.

A simple means for controlling the withdrawal of the mandrel and springfrom the bath is illustrated in FIG- URE 4 wherein cam 36 operates oncam follower 37 carried by arm 38 for raising the mandrel. It isunderstood 4 that in practice, a large number of mandrels are supportedfor a simultaneous handling. After dip-coating, the work (P.V.C. body)is heat treated for fusing the plastic. All this is conventional indip-coating.

Any desired spring shape can be selected. In all cases, the mandrel isso designed that a spring can be attached to a mandrel by friction. Withplastic material deposited about the mandrel above anchor turns 13 and14, a plastic skirt will be created which will more than cover any baredwires to be connected.

The completed connector is removed from its mandrel. The shape of theconnector housing makes it possible to blow a connector free of amandrel by compressed air passing through an axial bore in the mandrel.

Various mandrel shapes are possible. So long as the mandrel fills theregion within helical spring connector portion 10, no plastic cansurround the wire so that the spring metal bearing on the mandrelsurface will remain uncoated. By having clearance between the mandreland the anchor turns, the plastic material can enclose and bond to theprimed metal. Because of the twisting of wires when used in a connector,the absence of a strong bond to metal may result in the spring beingdisconnected from the plastic housing body. It is possible to provide alarge number of anchor turns and omit the priming.

The gauge of spring wire can be about the same as that of Wireconnectors now available. In contrast to such wire connectors nowavailable, the spring wire gauge can also be heavier because of thefreedom of individual spring coils to move or shape themselves. Thus thecoils of the spring in the new connector can move axially of the helicalspring to accommodate irregularities of the Wires to be connected. Alsothe coils can increase in diameter locally to accommodate the wiresbeing connected. Thus if there is an enlargement in the wires beingconnected, the spring coils can successively accommodate themselves asthe wire connector is twisted and after the obstruction has been passed,the wire coils can contract to normal size. As a result, the newconnector can have many more spring coils over a length of wires to bejoined than a conventional wire connector whose spring coils are fixedfor diameter or pitch or both.

In wire connectors, the direction of turning of the wire connector withrespect to wires to be connected is such that when turning a wireconnector to tighten it there is a tendency (which is resisted inconventional wire connectors by the rigid body) to create forces toexpand or open one or more spring coils. This tendency for expanding thespring coils comes into play particularly when the shape or arrangementof wires being connected tends to bind in the helical spring coils. Aconventional Wire connector will bind in such cases and prevent the Wireconnector from being fully applied. In such case, the use of pliers maybe relied upon to turn the connector, in which case the rigid insulatingbody is frequently cracked. If no attempt is made to turn such wireconnector any further, there is a possibility that the wire connector isnot fully positioned and may permit Wires to work loose under vibrationor will provide insufiicient contact area for the wires and spring.

By contrast, the new wire connector with a flexible housing body can beturned over wires and permits the spring coils to expand their diameteror even to move laterally of the entire helical spring and pass theblock or obstruction. As the new wire connector progresses along thewires being connected, the particular coils which may have expanded orwhich may have moved laterally can assume their normal condition andposition. Consequently, the new wire can be turned, and withoutexcessive force, to an end position where wires to be joined are wellwithin many coils of the helical spring. with the spring coils exertinga compressive force upon the wires to establish good electrical contactover large areas of wire and spring.

T e new Wire connector with flexible housing can be turned by handwithout tools and without the need for great force. The adaptability ofthe spring coils with regard to coil diameter, and lateral movement ofcoils, thus assures that the new wire connector, when turned by hand,can be turned to a final position where the wire connector is moved tothe limit of its travel. As a result of this adaptability, the new wireconnector can use heavier gauge wire for the helical spring as comparedto conventional wire connectors. Furthermore, one particular size of newwire connector provided with a flexible housing can cover a greaterrange of connector requirements than is true of conventional wireconnectors.

The new wire connector with flexible housing provides a still furtheradvantage in some applications, such as in lighting fixtures, householdappliances, and the like. In such devices, the new wire connector with aflexible housing will function to dampen any vibration or 60-cycle humwhich may be present. Thus, for example, in ballasts for fluorescentlighting, a 60-cycle hum may be accentuated by a rigid insulatinghousing for a wire connector providing a vibration conducting pathbetween the ballast core and the sheet metal of the fixture.

What is claimed is:

A method of making a wire connector comprising winding a length ofspring wire to provide multi-coil tapered helix connector portion and aco-axial anchor portion having at least one helical coil extending awayfrom the large end of said connector portion helix along the axisthereof, said anchor portion having the coil diameter significantlylarger than warranted by the connector portion helix taper, priming thewire of the anchor portion only with a coating of epoxy resin, disposingthe entire length of spring wire having the aforementioned shape overthe tapered end of a mandrel of good heat conducting metal and shaped sothat the tapered end of the mandrel provides a snug friction fit withinthe coils of the connector portion only, the mandrel portion within theanchor coil portion being small enough to provide annular clearancebetween the mandrel surface and anchor portion metal, said mandrel beinglonger than the overall length of the shaped wire to leave a mandrel endportion clear beyond the anchor portion of the shaped wire, positioningsaid mandrel so that its length is vertical with the tapered endcarrying the shaped wire being at the bottom, moving the mandrelvertically down into a molten bath of vinyl plastic to immerse theentire length of shaped spring wire into said bath and then raising saidmandrel from the bath at a predetermined rate, to permit molten plasticto congeal about the shaped metal, said mandrel raising the entirelength of spring wire together with the congealed mass of plastic, saidmandrel conducting heat from the bath to atmosphere to congeal themolten plastic and create a plastic shroud which covers the small end ofthe connector heliv portion and extends along the outside only of theconnector portion toward the anchor portion and continues along both theinside and outside of the anchor coil portion and about the wire makingup the anchor coil portion to embed such anchor coil portion wire, theplastic being firmly cemented to the anchor coil portion wire, andthereafter removing said finished wire connector from the tapered end ofsaid mandrel.

References Cited by the Examiner UNITED STATES PATENTS 2,110,458 3 3 8Applegate l7487 FOREIGN PATENTS 637,564 3/62 Canada.

JOHN F. BURNS, Primary Examiner. JOHN P. WILDMAN, E. JAMES SAX,Examiners.

